Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $42.78   7.667%   $46.0599   $46.06   $46.05   $46.10  
  Purchase #2 $122.27   8.577%   $132.7571   $132.76   $132.75   $132.80  
  Purchase #3 $163.49   13.566%   $185.6691   $185.67   $185.65   $185.70  
  Purchase #4 $212.71   11.219%   $236.5739   $236.57   $236.55   $236.60  
  Purchase #5 $232.41   3.105%   $239.6263   $239.63   $239.65   $239.60  
  Purchase #6 $224.28   5.278%   $236.1175   $236.12   $236.10   $236.10  
  Purchase #7 $84.32   6.825%   $90.0748   $90.07   $90.05   $90.10  
  7 purchase totals = $1,082.26       $1,166.8786   $1,166.88   $1,166.80   $1,167.00